Increased frequency of intermetatarsal and submetatarsal bursitis in early rheumatoid arthritis: a large case-controlled MRI study

Table 1 Baseline characteristics of all participants

	RA	Other arthritides¹	P value, RA vs other arthritides	Healthy controls	P value, RA vs healthy controls
	n = 157	n = 284		n = 193
Clinical features
Age, mean (SD)	59 (14)	56 (17)	0.07	50 (16)	< 0.001
Female, n (%)	109 (69)	158 (56)	0.005	136 (71)	0.83
BMI, mean (SD)	26 (5)	27 (4)	0.52	25 (4)	0.003
Symptom duration, in weeks, median (IQR)	10 (5–28)	8 (4–26)	0.13	NA	NA
Swollen joint count, median (IQR)	7 (2–11)	2 (1–4)	< 0.001	NA	NA
CRP, mg/L, median (IQR)	9 (4–26)	6 (3–16)	< 0.001	NA	NA
RF positive, n (%)	106 (68)	51 (18)	< 0.001	NA	NA
ACPA positive, n (%)	87 (59)	69 (25)	< 0.001	NA	NA
MRI features
Mean number of lesions per patient, n (SD)
Intermetatarsal bursitis	1.6 (1.4)	0.6 (1.0)	< 0.001	0.2 (0.7)	< 0.001
Submetatarsal bursitis	0.4 (0.8)	0.07 (0.3)	< 0.001	0.04 (0.2)	< 0.001
Morton’s neuroma	0.4 (0.6)	0.06 (0.3)	< 0.001	0.03 (0.2)	< 0.001
Diffuse submetatarsal alterations	0.5 (1.1)	0.3 (0.9)	0.068	0.3 (0.9)	0.092

RA rheumatoid arthritis, SD standard deviation, BMI body mass index, IQR interquartile range, CRP C-reactive protein, RF rheumatoid factor, ACPA anti-citrullinated peptide antigen (anti-CCP), MRI magnetic resonance imaging, NA not applicable
¹This group included the following diagnoses: unclassified arthritis (n = 148), psoriatic arthritis or spondyloarthritis (n = 45), inflammatory osteoarthritis (n = 23), reactive arthritis (n = 7), crystal arthropathy (n = 21), remitting seronegative symmetrical synovitis with pitting edema (n = 12), and other diagnoses (n = 28)

ISSN: 1478-6362